The use of plastic banding is well known for sealing containers of medicine, foodstuff, drink, toiletries and similar products to make them tamper-proof or tamper-evident. Heat-shrinkable bands may also be used for purposes of labeling containers, and for packaging purposes for example to fasten several articles together. A machine suitable for such banding purpose is shown in my U.S. Pat. No. 3,924,387 issued on Dec. 9, 1975, the entire disclosure of which is incorporated herein by reference. Other patents which disclose methods and apparatus for banding are my U.S. Pat. Nos. 4,318,685 and 3,974,628. The banding machines disclosed in such patents while useful, are not capable of operating at rates as high as desired by high speed commercial product packagers.
In an efficient packaging operation it is essential that the banding apparatus be capable of keeping up with the speed or rate at which the containers are being filled, and are hence ready for sealing or labeling. This makes it desirable to have apparatus which is capable of banding containers at rates as high as 600 containers per minute. Moreover, it is desirable to use film which is as thin and as short as possible in order to minimize the cost of the banding material. Since the containers are normally moved to the banding station, and from there to a heating tunnel for shrinking the band by a continuously moving conveyor, the containers could move continuously, were the banding operation not intermittent. That is, prior art machines must stop the container at the banding station for a sufficiently long time to enable the machine to place a band over the container by the stationery band placement mechanism. Although designing a moving banding mechanism, i.e. one that moves along the conveyor with the container, is technically feasable, it would have to be complex and hence costly to manufacture. When the containers to be banded are moved by a conveyor at high speed and are slowed for banding purposes by a feed screw with a dwell time, they tend to jiggle. This often causes the bands to fall off, instead of landing directly over the containers. Moreover, containers with lips or other protrusions will also prevent the plastic sleeves from falling directly over the containers. The higher the speed at which the containers are moved past the stationery banding station, the greater the likelihood that the bands will not fall squarely over the containers, causing the containers to be improperly sealed.